Generally, data access and storage systems consist of one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. Disks are rigid platters that are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, two or three disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
The only other moving part within a typical HDD is the head stack assembly. Within most HDDs, one magnetic read/write head or slider is associated with each side of each platter and flies just above or below the platter's surface. Each read/write head is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid arm apparatus that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single armature unit.
Each read/write head scans the surface of a disk during a “read” or “write” operation. The head and arm assembly is moved utilizing an actuator that is often a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the disk spindle is also mounted. The base casting is in turn mounted to a frame via a compliant suspension. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop directly over the desired track. The data on the spinning media is then read via a magnetic read sensor (typically magnetoresistive) on the read-write head.
As the storage capacity of DASDs continues to increase, a single disk drive enclosure may encounter many different kinds of applications. For example, a drive may be required to perform a very high throughput sequential operation, or a very high input/output rate random operation. Although there is no present manner of optimizing performance based upon any particular access characteristics, U.S. Pat. No. 5,293,282, discloses a disk drive with multiple actuators. The multiple actuators have multiple heads that read data from and write data to all tracks on the surfaces of the disks. The positioning of each head by respective actuators is controlled by embedded servo information recorded in the data tracks. Utilizing two actuators provides increased data transfer rates and reduced access times with respect to the access times provided by disk drives having a single actuator.
U.S. Pat. No. 6,563,657 discloses a hard disk drive for a computer system having at least two actuators for reading data from or writing data to the disks. The actuators may be configured to support the different methods of data access required of them. For example, if large quantities of sequential data are performed, one operation uses both actuators to increase throughput. However, if mostly random operations are to be performed, then independent usage of the actuators is preferred. These two methods of usage can be supported simultaneously, and can even be dictated by the user. The tracking format of the actuators can be configured such that the next logical track is physically located under a head on a different actuator to improve sequential operation. The actuators may also be utilized in a dual-channel configuration so that data can be written to both actuators at the same time, or read back at the same time to improve throughput. In addition, either of these configurations can be selected on a transfer-by-transfer basis by the user
Referring to FIG. 1, a schematic drawing of an information storage system, such as a direct access and storage device (DASD), comprising a magnetic hard disk file or drive 100 for a computer system is shown. Drive 100 has an outer housing or base 101 containing a plurality of stacked, parallel magnetic disks 102 (four shown) which are closely spaced apart. Disks 102 are rotated in unison about a central drive hub 103 by a spindle motor (not shown) located there below.
Drive 100 is also provided with multiple actuators 104 (two shown). Although both actuators 104 are shown mounted to the common shaft of a single pivot cartridge assembly 105, actuators 104 may be independently mounted to base 101 on separate support structures. Each actuator 104 comprises a plurality of stacked, parallel actuator arms 106 (three shown) in the form of a comb that is pivotally mounted to base 101 about pivot cartridge assembly 105. A controller (not shown) is also mounted to base 101 for selectively moving the comb of arms 106 relative to disks 102.
Each arm 106 has extending from it one or two parallel, cantilevered load beams or suspensions 107, and a head gimbal assembly (HGA) 108 having at least one magnetic read/write head secured to each suspension 107 for magnetically reading data from or magnetically writing data to disks 102. Suspensions 107 have a spring-like quality which biases or maintains them in parallel relationship relative to one another. Motor voice coils 109 housed within respective dual magnet assemblies 110 are also mounted to the combs of arms 106 opposite head gimbal assemblies 108. Operation of the respective motor voice coils 109 is independently controlled. Movement of a motor voice coil 109 moves head gimbal assemblies 108 radially across tracks on the disks 102 until the heads on head gimbal assemblies 108 settle on the target tracks. A ramp 111 is provided near the perimeter of disks 102 for supporting head gimbal assemblies 108 while drive 100 is not in operation.
The operations of actuators 104 can be configured to support the different methods of data access required of them. For example, if large quantities of sequential data are performed, one operation uses both actuators 104 in parallel to increase throughput. However, if mostly random operations are to be performed, then independent usage of the actuators is preferred. These two methods of usage can be supported simultaneously, and can even be dictated on a selected basis by the user.